The processing of animal carcasses, which usually takes places right after slaughtering, usually involves the step of scalding the carcass to remove dirt and other contaminants. In the case of hog carcasses, the scalding also softens the hair and opens the hair pores in the skin so that the carcass can be dehaired. In the past, this process has been carried out using relatively primitive equipment. Elongated tanks or vats holding hot water were provided, and carcasses were simply dumped in one end of the tank and floated, pushed, or dragged along to the other end. In some cases some form of agitation was provided. In other cases some primitive form of movement device such as a drag chain was provided for pulling the carcasses through the tanks.
In most cases some water from the tank was removed and other water was added, either periodically or continuously. It will however be appreciated that, a short while after processing has been commenced, the water in the tank will be substantially contaminated with dirt and other contaminants from the skin and hair, and faecal and fluid discharges of carcasses that have already been processed. As a result, although the carcasses were processed through the tanks, when they exited from the other end, the carcasses still carried some of the contamination which was inevitably present in the water in the tanks from preceding carcasses.
An improved form of carcass washing apparatus is shown in U.S. Pat. No. 4,829,637, inventor Lyle W. Norrie, and assigned to Knud Simonsen Industries Limited. In that patent, apparatus was provided consisting of a chamber with an overhead conveyor rail, and a system of water showers or sprays extending along the upper region of the chamber adjacent the conveyor. Beneath the conveyor there was provided a system of angle supports with movement means on such supports. In this way, when the carcasses were supported on the overhead conveyor rail, they lay at an angle on one or other of the supports. The movement means on the supports and on the conveyor rails moved at the same speed so that the carcasses were progressively washed on one side, and then on the other side.
Water was collected beneath the supports, filtered, reheated and recycled back to the upper region of the chamber so that it could continuously be reused. In this way, the continuous filtration of the water and the continuous heating of the water provided that substantially clean water would be used for washing and scalding each carcass so that contamination was substantially reduced by the time the carcass had been fully processed through the apparatus.
However, this apparatus had one disadvantage, namely that the carcasses were supported on one side, while the other side was exposed to the shower or water spray coming downwardly within the chamber. As a result, while one side was being cleansed and processed, the other side was not being processed to the same extent, Consequently, the carcasses would have to be processed for a considerable length of time before they were completely cleaned and scalded. In addition, the provision of the movement means on the lower supports added to the expense of the overall apparatus and involved maintenance and consequent down time which was somewhat of a disadvantage.
Clearly, it is advantageous if the scalding of carcasses can be carried on in apparatus such that the carcass is scalded on substantially all surfaces simultaneously, so that all contamination is washed downwardly off the carcass, from all sides, at the same time.
However, this type of facility must also be designed with certain other considerations in mind. In the first place, the carcasses must be processed for a sufficient length of time to provide the desired end result, namely a clean and fully scalded carcass, and preferably in the case of hogs, a carcass where the hairs have been softened and the skin hair pores opened sufficiently uniformly over the entire carcass to permit hair be easily removed. In order to this, it is apparent that the carcasses when they enter the facility will be carrying the maximum of dirt and contamination. It is desirable that this shall be washed off and removed, and the carcass then re-scalded further, in fresh, heated water, in a series of stages, so that as far as possible the carcasses shall be passed through successive stages of washing in which, in each stage, the water is cleaner than in the previous stage.
In each stage, the water is desirably filtered, so that as far as possible the contamination that is present in that stage is continuously removed, and the water is maintained at each stage at a desired process temperature. The process temperature, may vary from one stage or zone of the apparatus to another.
Preferably in order to achieve this type of result there will be two (or in some cases more) cleaning or scalding zones, with each one separate from the next, and arranged so that the water circulating within any one zone is substantially prevented from entering the downstream zone(s), although it may be recycled to the previous more dirty zones, upstream.
However, this in turn creates a whole new series of problems. In order to achieve the necessary cleansing and scalding of a carcass in any one zone it is necessary that the carcass should remain in that zone for a predetermined length of time, herein referred to as the "dwell" time. This dwell time can be achieved either by letting the carcass remain stationary, ,within a relatively short zone, or alternatively by moving it continuously through a zone of much greater. length. The latter system is preferable since it enables the continuous processing of carcasses one after the other on a continuously moving conveyor system. This in turn enables the processing work to be carried out in the most efficient continuous manner, both upstream and downstream of the washing and scalding operation, and leads to overall economies in the operation in the entire process.
It does however produce its own series of problems. Thus the conveyor should preferably move at a predetermined speed, synchronized with the movement of conveyors relative to the rest of the processing facility. In other words it is not usually desirable to move a conveyor at a first speed in one part of the system and a second much slower speed at another part of the system, without allowing for the accumulation of carcasses in batches between one portion of the process and the next. Thus given a certain desired processing line speed, then it may be necessary to provide cleansing and scalding facilities in the form of several zones which extend along a substantial linear distance of the conveyor system. This in turn can require the occupation of a considerable length of a building which may be both inconvenient and expensive. In addition, it is desirable that the pumping and the heat exchange and filtering facilities for maintaining the conditions of the water within each of the various separate zones, is as far as possible at a centralized location so that it can all be controlled and monitored and serviced in a simple and economical manner.